1. Technical Field
The present invention relates to a unitized oil seal and a method of making unitized oil seals. More particularly, two sealing elements are respectively connected to inner and outer seal cases such that each sealing element engages a relatively rotatable axially-extending circumferential surface formed on the other seal case.
2. Brief Description of the Background Art
Elastomeric unitized oil seals have long been used in automotive applications because the seal case protects the sealing elements during shipment and installation. An oil seal should be easy to assemble and install as well as durable and reliable. In aftermarket repair facilities, methods used to install unitized oil seals vary considerably.
In some instances, improper tools and improper installation techniques are used which can damage the sealing elements. If an elastomeric seal is installed and not properly lubricated after installation, the seal will wear excessively.
When a unitized seal lip is molded of an elastomer which is formed in situ within a unitized seal cartridge, it is virtually impossible to visually inspect the seal lip which is located within the cartridge. Such unitized seals are difficult to nondestructively test in production.
Polytetrafluoroethylene (PTFE) seals offer advantages of low start-up and running torque and may be well-known techniques. Moreover, PTFE seals are self-lubricating and thereby minimize the need for lubrication. In prior art PTFE seal designs, a single PTFE wafer is typically used to line or form the primary seal element. An auxiliary sealing element, or dirt excluder element, may be formed of an elastomeric material. Both the PTFE lined primary seal element and the auxiliary element are normally formed on the same seal case and engage another seal case to form a unitized seal cartridge. Assembly of composite elastomeric and PTFE unitized seals is complicated and visual inspection of the seal elements is precluded by the unitized construction of the seal.
These and other problems are overcome by the unitized oil seal of the present invention.